Audiphone



. I 1,49 ,919 M. L BELLUS June 10, 1924.-

AUDIPHONE Filed Ndv. 2 1921 Patented June 10, 1924.

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MARTIN L. BELLUS, OF CHICAGO, ILLINOIS.

AUDIP HONE.

Application filed November 2, 1921. Serial No. 512,283.

T 0 all whom it may concern.

Be it known that I, MARTIN L. BnLLUs, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented new and useful Improvements in Audiphones, of which thefollowing is a specification. I p

This invention relates to transmitters for audiphones, and its object isto provide a device ofthis kind embodying certain novel features ofconstruction and modes of operation to be described in detailhereinafter. r

In order that the invention may be better understood, reference, is hadto the accompanying drawing forming a part of this specification, and insaid drawing:

Figure 1 is a central "ertical section of the device, and

Fig. 2 is an elevation with one of the end caps removed.

Theinvention contemplates the use of two carbon diaphragms and anelectrode for each diaphragm. The diaphragms are shown at 10 and theelectrodes at 11. Each electrode consists of a disk or block of carbonhaving a number of pockets containing carbon granules 12 which areadapted to contact with the diaphragms in the usual manner, so that thevibrations produced in'th'e diaphragm by the sound-waves varies thepressure at the v multitude of contacts between the granules, and thusvaries the'resistance of the circuit, as is well understood in the art.

The instrument includes a casing consisting of an intermediate portion13 and end caps 14. The intermediate portion is annular and has reducedand exteriorly threaded end portions 15 on which the caps are screwed.The diaphragms 10 are clamped between the caps 14 and the edges of theend portions 15, with gasket rin s 16 interposed therebetween. Theintermediate portion of the casing is made of metal, whereas the capsare made of hard rubber, and the latter are perforated, as shown at 17for entrance of the sound-waves.

The electrodes 11 are supported by a. metallic spider consisting of anumber of arms 18, four being shown, radiating from a hub 19. Oneelectrode is fastened to one side of the spider hub and the otherelectrode is fastened to the other side of the spider hub. The fasteningmeans for the electrodes may be a centrally located bolt 20. Theelectrodes are therefore positioned between the diabeing behind theother diaphragm.

The outer ends of the spider arms 18 are phragms 10, the outer face ofone electrode having the pockets containing the granules 12 being behindone diaphragm, and the corresponding face of the other electrode securedby screws or other suitable fasteners 21 to the ring-like intermediateportion 13 of the casing, the same having flanges 22 on theinside-against one side'of which the extremities of the spider arms seatandthrough which the fasteners 21 pass.

The spider arms 18 are insulated from the ring 13 by disks 23 ofinsulating material interposed between the fianges 22 and theextremities of the arms, and disks and sleeves of insulation 23 betweenthe flanges and the fasteners 21.

To two adjacent flanges 22 are also fastened connectors 24 and 24whereby the instrument is connected to the terminals of the battery (notshown). The connector 24 is in electric contact with its supportingflange, whereas the connector24 1S'1I1S11l21t6d from its supportingflange by a strip 25 of insulation. The ring 13 has edge slots 26through i which the connectors 24' and 24 extend to the outside of thecasing forattachment to the battery terminals.

The'two wires'leadin'g to the receiver are shown at 27 and-28, the sameentering through an edge aperture 29 in the ring 13' midway between'tl1eslots'26.' Wire 27 is electrically connected to one of the spider arms18 by its fastener 21, and it is insulated from the ring 13 by theinsulation disk and sleeve 28 of said fastener. The wire 28 iselectrically connected to the insulated connector 24 by one of thescrews or other fasteners 29 by which said connector is secured to thering flange, the wire being insulated: from said flange by a disk andsleeve 29? of insulation under the head of and around the screw. i

The circuit through the instrument is by the way of the non-insulatedconnector 24 to the ring 13, to diaphragms 10, electrodes 11, spider arm18 to which wire 27 is electrically connected, by wire 27 to receiver,and from receiver by wire 28-to connector 24*. It is to be understood,ofcourse, that the connector 24 is attached to one battery terminal andthe connector 24 to the other battery terminal. The receiver has notbeen illustrated as it forms no part of the present inventioii. Byreference to Fig. 2 it will be seen that the connectors 24: and 24*extend to the terminals of a source of current.

The manner of attaching the two electrodes 11 on the same spider is adecided advantage for the reason that both electrodes receive the sameamount of flow of electric current. The spider is mounted midway betweenthe edges of the ring 13, which locates the electrodes between thediaphragms 10 and renders practical the use of two such with anelectrode for each. The space between the ,diaphragms forms apractically air-tight sounding chamber which eliminates metallic sounds,and also equalizes the pressure on the diaphragms. In other words, thefront diaphragm acts as the back wall of the sounding chamber of theback diaphragm, and vice versa, the back diaphragm acts as a back wallfor the sounding chamber of the front diaphragm, and as these walls arenot formed of rigid metal but are flexible, metallic sounds are entirelyeliminated.

A further advantage oi the arrangement of the two diaphragms andelectrodes .is that the instrument is operative irrespective of theposition in which it is held, as the carbon granules 12 on the sidetoward which the instrument may be tilted will be in contact with theopposite diaphragm. With a single diaphragm and electrode, theinstrument is rendered inoperative or very inefficient if it is tiltedin a direction to cause the granules to recede from the diaphragm. Itwill be evident that this position of a double-diaphragm instrumentwould not render it inoperative because no matter how the instrumentmight be tilted, the diaphragm on one side would obtain the contact ofthe granules back of the same. The single casing employed renders theinstrument very compact and it can be kept within the same dimensions asa single-diaphragm instrument. The invention results in a doubletransmitter in a single case, and gives double the sounding space anddouble the area of the diaphragm. By the double electrodes a greaterresistance is obtained, which adds materially to the life of the batteryused with the instrument, and as the amount of granules used is alsodoubled, a greater number of points of contact are obtained, whichincreases the power of the instrument and makes it louder than asingle-diaphragm and electrode instrument. This also permits the use ofa battery of a higher voltage than is possible with the usual type 01single instruments, and hence the power of the instrument iscorrespondingly increased.

A further advantage resulting from the duplication of the electrodes andassociate elements, is that if one side of the instrument should bedisabled, the other side will continue to work. If a single diaphragminstrument becomes disabled by the granules wedging between theelectrode and the diaphragm, the instrument is thrown out of commissioncompletely.

I claim:

In an audiphone transmitter, a casing having sound entrance apertures atits ends, diaphragms in the casing behind thewapertured ends thereof andspaced from each other, a spider in the casing and consisting of acentral hub and arms radiating therefrom, the outer ends of the spiderarms being secured to the casing. and insulated therefrom, and separateand electrically connected electrodes secured to opposite sides of thespider hub andfacing in opposite directions, one electrode beingpositioned in operative relation with respect to one diaphragm and theother electrode being posisitioned in operative relation with respect tothe other diaphragm.

In testimony whereofl afllx my signature.

IVTARTTN L. BELLUS.

